Berkeley database handling examples:

DB *open_db (const char *f, bool dup = false) {
  DB *dbp = 0;
  int r = db_create (&dbp, NULL, 0);

  if (r != 0)
    {
      printf ("db_create: %s\n", db_strerror (r));
      exit (1);
    }

  if (dup)
    if (dbp->set_flags (dbp, DB_DUPSORT) != 0)
      {
        cout << "Couldn't set duplicate records for database" << endl;
        exit (1);
      }

  if ((r = dbp->open (dbp, NULL, f, NULL, DB_BTREE, DB_CREATE, 0664)) != 0)
    {
      dbp->err (dbp, r, f);
      dbp->close (dbp, 0);
      exit (1);
    }
  return dbp;
}

void stor_string (DB *dbp, int32_t id, const dynstr *s)
{
  DBT dkey, data;
  memset (&dkey, 0, sizeof (DBT));
  memset (&data, 0, sizeof (DBT));

  dkey.data = &id;
  dkey.size = sizeof (int32_t);

  data.data = s->str;
  data.size = s->len + 1;

  int r = dbp->put (dbp, NULL, &dkey, &data, 0);
  if (r != 0) {
    cerr << "Database put failed: " << id << " => " << s << endl;
    exit (1);
  }
}

void del_entry (DB *dbp, int32_t id)
{
  DBT dkey;
  memset (&dkey, 0, sizeof (DBT));
  dkey.data = &id;
  dkey.size = sizeof (int32_t);
  dbp->del (dbp, NULL, &dkey, 0);
  // FIXME: check returnvalue
}

bool retr_string (DB *dbp, int32_t id, dynstr *&s)
{
  DBT dkey, data;

  memset (&dkey, 0, sizeof (DBT));
  memset (&data, 0, sizeof (DBT));

  dkey.data = &id;
  dkey.size = sizeof (int32_t);

  int r = dbp->get (dbp, NULL, &dkey, &data, 0);
  if (r != DB_NOTFOUND) {
    s = new dynstr ((char *)data.data, data.size - 1);
    return true;
  }
  return false;
}